In the LTE system, a downlink dedicated pilot frequency is used as a phase reference for demodulating a physical downlink shared channel (PDSCH), and is configured semi-statically for a user terminal by a higher layer. The downlink dedicated pilot frequency is transmitted through the antenna port 5, and in current LTE versions, main application contexts include downlink reference signal formed by a beam, downlink reference signal pre-encoded specifically, and parallel load.
The pattern of the downlink dedicated pilot frequency in the extended cyclic prefix (Extended CP) frame structure is determined in 3GPP (3rd Generation Partnership Project) LTE 52bis conference and 53# conference, and is illustrated in the reference 3GPP R1-2159, which specifies:
Extended cyclic prefix:
                                                        a                              k                ,                l                                            (                p                )                                      =                          r              ⁡                              (                                                      4                    ·                                          l                      ′                                        ·                                          N                      RB                      PDSCH                                                        +                                      m                    ′                                                  )                                              ⁢                                          ⁢          k          =                                                    (                                  k                  ′                                )                            ⁢                                                mod                  ⁢                  N                                SC                RB                                      +                                          N                SC                RB                            ·                              n                PRB                                                    ⁢                                  ⁢                              k            ′                    =                      {                                                                                                      3                      ⁢                                              m                        ′                                                              ,                                                                                                              if                      ⁢                                                                                          ⁢                      l                                        =                    4                                                                                                                                                                  3                        ⁢                                                  m                          ′                                                                    +                      2                                        ,                                                                                                              if                      ⁢                                                                                          ⁢                      l                                        =                    1                                                                                                          Formula        ⁢                                  ⁢        1                                l        =                  {                                                                                          4                                                                                                      l                        ′                                            ∈                                              {                                                  0                          ,                          2                                                }                                                                                                                                  1                                                                                                      l                        ′                                            =                      1                                                                                  ⁢                                                          ⁢                              l                ′                                      =                          {                                                                                                                                                                        0                            ,                                                                                                                                                              if                              ⁢                                                                                                                          ⁢                                                              n                                s                                                            ⁢                              mod                              ⁢                                                                                                                          ⁢                              2                                                        =                            0                                                                                                                                                                            1                            ,                            2                            ,                                                                                                                                                              if                              ⁢                                                                                                                          ⁢                                                              n                                s                                                            ⁢                              mod                              ⁢                                                                                                                          ⁢                              2                                                        =                            1                                                                                                                ⁢                                                                                  ⁢                                          m                      ′                                                        =                  0                                ,                1                ,                …                ⁢                                                                  ,                                                      4                    ⁢                                          N                      RB                      PDSCH                                                        -                  1                                                                                        Formula        ⁢                                  ⁢        2            
Wherein, αk,l(p) represents a downlink dedicated pilot frequency a, k is a frequency domain mapping position of the dedicated pilot frequency in a physical resource block (RB) allocated on the PDSCH, and l is a time domain mapping position of the dedicated pilot frequency in the RB allocated on the PDSCH; l′ and m′ are intermediate variables, ns is a time slot, NRBPDSCH is the number of physical resource blocks allocated for the UE on the PDSCH, NSCRB is the number of sub-carriers included in each minimal physical resource block, and nPRB is the serial number of a physical resource block allocated for the UE on the entire bandwidth of the PDSCH.
From the
      k    =                            (                      k            ′                    )                ⁢                              mod            ⁢            N                    SC          RB                    +                        N          SC          RB                ·                  n          PRB                      ,          ⁢            k      ′        =          {                                                                                    3                  ⁢                                      m                    ′                                                  ,                                                                                      if                  ⁢                                                                          ⁢                  l                                =                4                                                                                                                              3                    ⁢                                          m                      ′                                                        +                  2                                ,                                                                                      if                  ⁢                                                                          ⁢                  l                                -                1                                                    ,                                  ⁢                              and            ⁢                                                  ⁢                          m              ′                                =          0                ,        1        ,        …        ⁢                                  ,                              4            ⁢                          N              RB              PDSCH                                -          1                    in the above formulas, it can be seen that the frequency domain position of a downlink dedicated pilot frequency in a RB allocated on the PDSCH is relatively fixed, and if the beam directions of two adjacent cells are on the same line and positions of the dedicated pilot frequencies in the frequency domain are the same, comparatively large peak power will be generated for users at edges of the cells and the interference between UEs in different cells will be increased.